The enhancement of hydration of fluidized bed combustion ash by sonication.

The use of limestone to control SO2 emissions in fluidized bed combustors (FBC) results in high CaO content in the ashes. This presents challenges for their disposal including significant exothermic behavior and uncontrolled expansion in the landfill. Hydration of the ashes is required to convert the CaO, but the current two-step hydration process is not very effective. In the present work a new technique using ultrasound to promote the hydration was examined. Initial work was done using an ultrasonic bath and subsequently an ultrasonic probe. Hydration levels greater than 80% in 20-40 min with amplitudes of 40% or more were achieved with residues containing high levels of CaO. This is about twice what can be achieved using conventional hydration technique. Similar results were obtained using FBC ashes from four utility/industrial scale and one pilot plant scale FBC units. The mechanism for the promotion of hydration bythe ultrasound is also explored.

Stereospecificity of Pseudomonas fluorescens kynureninase for diastereomers of beta-methylkynurenine.

The diastereomers of beta-methyl-L-kynurenine were prepared by preparative ozonolysis of the respective diastereomers of beta-methyl-L-tryptophan. A practical method for preparative enzymatic resolution of the diastereomers of beta-methyltryptophan was developed using carboxypeptidase A digestion of the N-trifluoroacetyl derivatives. The stereochemical assignment was confirmed by X-ray crystal structure determination of (2S, 3R)-threo-beta-methyl-L-tryptophan. (2S,3S)-erythro-beta-Methyl-L-kynurenine is a slow substrate for kynureninase from Pseudomonas fluorescens (k(cat)/K(m) = 0.1% that of L-kynurenine), producing anthranilic acid, while (2S,3R)-threo-L-kynurenine is about 390-fold less reactive than erythro. Rapid-scanning stopped-flow measurements show that beta-methyl substitution affects the rate of alpha-deprotonation of the L-kynurenine-pyridoxal-5'-phosphate Schiffs base. This is consistent with the stereoelectronic requirements of the reaction. These results are the first demonstration that beta-substituted kynurenines can be substrates for kynureninase, and may be useful in the design of mechanism-based inhibitors.

How controlled stress affects healing tissues.

Restoration of a patient's full range of motion, strength, and function are the primary goals of occupational and physical therapy. Immobilization of normal connective tissue leads to biochemical, biomechanical, and physiologic changes within a week. These changes are magnified in the presence of trauma or edema, and they may create permanent damage if not addressed swiftly and properly. This is best accomplished by applying specific types of stress to the involved and associated structures at optimal intervals during the rehabilitation process. Load must be applied at adequate intensity and duration to successfully affect the viscous property of connective tissue. This is necessary to effect permanent elongation of the restricted tissues. Early controlled motion is vital to prevent the negative changes associated with immobilization and to maintain normal viscoelasticity and homeostasis of connective tissue. Hand therapists must have a thorough understanding of the changes associated with injured structures. Only then can they provide optimal stress delivery to facilitate restoration of function.

A bootstrap approach to medical decision analysis.

In economic evaluations of health treatments, the sensitivity of a cost-benefit (CB), cost-effectiveness (CE) or cost-utility (CU) analysis to changes in modeling assumptions, variation in data, and sampling error is important. The typical approach to this problem is ad hoc experimentation; namely, a few parameters of particular interest are changed, either separately or in combination, over plausible ranges. The impact of random variation in the data is seldom explored beyond parametric tests of the statistical significance of estimated coefficients. This note suggests a systematic approach to sensitivity analysis. Bootstrap sampling is used to determine to what extent the patients' response to treatment and economic consequences might vary due to many replications of a clinical trial.

Antiviral therapy for neonatal herpes simplex virus: a cost-effectiveness analysis.

Each year, about 1,600 infants in the United States are infected with neonatal herpes simplex virus. We conducted a cost-effectiveness analysis of antiviral drug therapy (acyclovir) for three forms of herpes simplex virus infection: skin, ear, and mouth (SEM), central nervous system (CNS), and disseminated multiorgan (DIS) disease. Five levels of patient outcomes were examined (normal, mild, moderate, severe, dead). We obtained information on disease occurrence and survival from clinical trials and historical reviews of untreated newborns. We considered approaches for treating all or any of the forms of the disease and compared them with no use of antiviral drugs. The main measure of effectiveness was lives saved, including those of descendants of survivors. Costs were measured from a societal perspective and included direct medical costs, institutional care, and special education. We used a discount rate of 3% and valued dollars at 1995 levels. We also considered the perspective of a managed care organization. From a societal viewpoint relative to no treatment, antiviral therapy for SEM resulted in a gain of 0.8 lives and a cost reduction of $78,601 per case. For the treatment of CNS and DIS disease, antiviral therapy saved more lives but at increased cost, with respective marginal costs per additional life saved of $75,125 and $46,619. From a managed care perspective, antiviral therapy is more cost-effective than from a societal viewpoint because costs of institutional care and special education are not the responsibility of managed care organizations. Development of at-home therapies will further improve the cost-effectiveness of antiviral therapy for neonatal herpes simplex virus infection.

Prognostic value of the CD4+ T cell count for HIV-1 infected patients with advanced immunosuppression.

The prognostic value of the CD4+ T cell count is not clearly established for HIV-1 infected patients with an advanced immunosuppression. The aim of this study was to assess the relationship between CD4+ T cell counts and survival in patients with less than 50 CD4+ T cells per mm3 (/mm3). We examined an historical cohort of 97 patients with 2 consecutive CD4+ T cells determinations < 50/mm3 within 3 months, followed at a university hospital of the University of Montreal. The proportion of men was 93% with 74% being homo/bisexual. The means of the 2 CD4+ T cell counts/mm3 were 25 and 25.1 respectively. Median survival after the first CD4+ T cell count < 50 CD4+ T cells/mm3 was 15.2 months. Using the proportional hazard model, the median survival of patients with 2 consecutive CD4+ T cell counts < or = 20/mm3 was 9.3 months compared to 19.2 for those with 20-50 CD4+ T cells/mm3 (P < 0.0001). It seems then, that the CD4+ T cell count is a helpful prognostic marker, even in very immunosuppressed patients. Its prognostic value is more accurate if the measurement is replaced within 1-3 months because of high variability at this level of immunosuppression.

Measures of clinical agreement for nominal and categorical data: the kappa coefficient.

The desire to determine the extent inter-rater measurements obtained in a clinical setting are free from measurement error and reflect true scores has spurned a renewed interest in assessment of reliability. The kappa coefficient is considered the statistic of choice to analyze the reliability of nominal and categorical types of data recorded on the same patient by more than one clinician. This paper presents a simple computer program written in PASCAL that can be used in a clinical environment to quickly determine the reliability of nominal or categorical data. This computer program calculates both weighted and non-weighted kappa coefficients with their corresponding standard errors as well as bias-correcting jackknife estimates of kappa for use with small sample sizes.

Obsessive and compulsive characteristics of alcohol abuse and dependence: quantification by a newly developed questionnaire.

The purpose of the this study was to develop an instrument for measuring the obsessive and compulsive characteristics of drinking-related thought and behavior in subjects who abuse or are dependent on alcohol, and to quantify the extent to which drinking-related thought and behavior in these subjects resemble the obsessions and compulsions seen in obsessive-compulsive disorder (OCD). To achieve these goals, the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was modified to reflect obsessionality and compulsivity specifically related to heavy drinking rather than to obsessions and compulsions generally. The modified Y-BOCS (Y-BOCS-hd) was administered to 62 subjects satisfying DSM-III-R criteria for alcohol abuse or alcohol dependence and 62 matched normal controls. The data showed that the Y-BOCS-hd is a sensitive and specific instrument for measuring the obsessive and compulsive characteristics of drinking-related thought and behavior in alcohol-abusing and alcohol-dependent populations, and that there are specific and quantifiable similarities between these characteristics and the obsessions and compulsions of OCD. The data also indicated that the Y-BOCS-hd may be a useful screening instrument for the presence of alcohol abuse and dependence.

Obsessive and compulsive characteristics of craving for alcohol in alcohol abuse and dependence.

The purpose of this study was to quantify the extent to which subjective ratings of craving for alcohol in the alcohol-abusing or dependent person (herein, alcoholic) correlate with measurable and specific characteristics of obsessions and compulsions. The Yale-Brown Obsessive Compulsive Scale modified to reflect obsessionality and compulsivity specifically related to heavy drinking (Y-BOCS-hd) was used for this purpose. Highly significant correlations were found in the alcoholic population (n = 62) between subjectively rated craving for alcoholic beverages and several of the Y-BOCS-hd questions regarding alcohol-related thoughts and drinking behavior. Additionally, mean craving scores were considerably greater in the alcoholic population than in the matched control population (n = 62). The data suggest that craving shares specific features in common with the obsessions of obsessive-compulsive disorder and that the existence of craving is dependent on the presence of obsessive thoughts about drinking. Positive correlations between craving and measures of compulsive drinking behavior also were found; compulsive drinking behavior, however, may reflect the consequences of craving rather than a fundamental characteristic of craving itself. The data show that despite difficulties in defining the term craving, it is clearly a phenomenon that is experienced or endorsed by most alcoholic subjects and is not by most persons who do not abuse alcohol.

Managing for change: a departmental quality improvement program (QIP).

The development and implementation of an integrated Quality Improvement Program (QIP) for the Department of Surgery at The Hospital for Sick Children was approached as a problem-solving process by which departmental managers could bring about change so that actual results would align more closely with desired outcomes. A planned and systematic process was developed, through which managers are able to reach decisions about when and where to make useful changes that result in improved quality of care and services provided. Three useful techniques were employed: team-building, continuing education and quality circles.

The clinical nurse specialist in a home healthcare setting.

An organizational model is proposed that allows for the optimal functioning of the clinical nurse specialist in a home healthcare agency setting.

Sequelae of SCI after discharge from the initial rehabilitation program.

The purpose of this study was to identify sequelae that occurred in persons with spinal cord injuries 11 weeks to 5 years after discharge from two initial rehabilitation programs. The investigator-developed instrument was first administered to a convenience sample of 21 subjects (Adamski, 1983). The modified version of the instrument was administered to a probability sample of 19 subjects in the present study. The results demonstrated that respondents experienced a higher incidence of medical sequelae than has been documented in the literature. These findings have important implications for nursing practice in developing and evaluating educational programs for persons with spinal cord injuries.

Comparison of statistical methods for the analysis of limiting dilution assays.

This study reports the results of a critical comparison of five statistical methods for estimating the density of viable cells in a limiting dilution assay (LDA). Artificial data were generated using Monte Carlo simulation. The performance of each statistical method was examined with respect to the accuracy of its estimator and, most importantly, the accuracy of its associated estimated standard error (SE). The regression method was found to perform at a level that is unacceptable for scientific research, due primarily to gross underestimation of the SE. The maximum likelihood method exhibited the best overall performance. A corrected version of Taswell's weighted-mean method, which provides the best performance among all noniterative methods examined, is also presented.